The present invention relates to a V-shape belt for transmitting driving force in a continuously variable transmission of an automobile.
More particularly, the present invention relates to improvements in a V-shape belt comprising a plurality of links and a plurality of V-shape blocks. Each link includes forward and backward ends, and the forward end of one link is rotatably connected to the backward end of an adjacent link by a pin.
Each V-shape block engages with at least one link, so that a continuous V-shape loop is formed. The V-shape loop engages with pulleys, and the V-shape loop transmits driving force from one pulley to another pulley. A conventional V-shape loop is disclosed in a copending application (Ser. No.: 11,336, filed on Feb. 5, 1987 now U.S. Pat. No. 4,767,333).
Also a similar V-shape loop is disclosed in Japanese Patent application Laid open Sho No. 59-226729. The V-shape block includes an opening for engaging with at least one link.
When the V-shape loop is spanned between pulleys, several V-shape blocks engage with grooves of the pulleys, and the other V-shape blocks are free and apart from the pulleys.
When the pulleys are rotated, the free V-shape block engages with the V-shape grooves of the pulley at intervals of a constant time period according to the rotational speed of the V-shape loop, and this engagement makes noise at the time of each engagement. Such noise is called pitch noise and the frequency of the noise is calculated by a formula as follows:
frequency of the noise=rotational speed of the V-shape belt.div.block pitch.
To prevent the pitch noise, the V-shape block of the conventional continuously variable transmission includes different shapes on contacting edges thereof, which engage with the V-shape grooves of the pulleys. Further, the different shapes of the contacting edges of V-shape blocks are arranged at random in the longitudinal direction of the V-shape belt. Accordingly, radial positions for engagement between the V-shape blocks and the V-shape grooves of the pulleys are irregularly varied. As a result, the time period for engagement between the V-shape blocks and the V-shape grooves of the pulleys is irregularly varied. Therefore, a peak of noise in a specific frequency is lowered, because frequency distribution is leveled.
However, the conventional V-shape belt needs at least two types of blocks which include different shaped contacting edges of the V-shape blocks in order to reduce the noise level.